In general, flat panel displays are roughly classified into light emission type displays and light reception type displays. Light emission type displays include flat cathode-ray tubes, plasma display panels, electroluminescence elements, fluorescent display devices, light emission diodes and the like. Light reception type displays include liquid crystal displays (LCD) and the like.
An LCD receives light from the outside to form an image, which is a characteristic of the light reception type displays. Therefore, on the rear of an LCD, a backlight assembly is installed so as to irradiate light.
In a general backlight assembly, high luminance, high efficiency, uniformity of luminance, long life span, slimness, low weight, low cost are required. In the case of a notebook computer, a highly-efficient lamp with a long life span is required so as to reduce power consumption. In the case of a monitor or TV, a lamp with high luminance is required.
FIG. 1 is a diagram schematically illustrating the construction of a conventional backlight assembly 100. As shown in FIG. 1, the backlight assembly includes a power supply section 110 composed of a rectifying section 111, a power factor correction (PFC) circuit 112, and a DC/DC converter 113; an inverter 120 composed of a plurality of transformers 122 and a controller 121 controlling the transformers 122; and a lamp unit 130 composed of a plurality of lamps connected to the transformers 122, respectively. As shown in FIG. 1, the backlight assembly 100 has such a structure that the power supply section 110 and the inverter 120 are separated from each other.
The rectifying section 111 converts alternating current (AC) input power into direct current (DC) input power. The PFC circuit 112 adjusts a power factor so as to convert the direct current input power, converted by the rectifying section 111, into direct current power having a predetermined magnitude (typically, 380 V), in order to enhance power efficiency of the backlight assembly. The DC/DC converter 113 converts the direct current power, converted by the PFC circuit 112, into direct current power having a predetermined magnitude (for example, 24 V) and simultaneously performs isolation between the power supply and the load.
Therefore, the DC/DC converter 113 outputs the isolated direct current power having a predetermined magnitude to the inverter 120.
A main function of the inverter 120 is to perform control such that a constant current is supplied to the respective lamps when and after the lamps are discharged, thereby minimizing a current deviation between the lamps.
Accordingly, in the conventional inverter 120, the plurality of transformers 122 are respectively connected to the lamps 130 and a secondary output current of each transformer 122 is constantly maintained, in order to implement the above-described function.
In the conventional backlight assembly, however, the power supply section 110 and the inverter 120 are separated from each other, so that there are difficulties in circuit design and production. Accordingly, productivity decreases, and power consumption increases.
Further, as one transformer is connected to only one lamp, the overall bulk of the circuit increases, and the efficiency of the power supply used for driving the conventional backlight assembly decreases. Further, as the lamps are directly connected to the transformers without a balancing circuit section, a luminous characteristic of the conventional backlight assembly decreases.